Android Camera2 Api 实现预览和拍照

三川小哥

算法优化工程师

camera2的结构如下，主要是通过相机管理器（CameraManager）获得相机设备（CameraDevice），然后再开启一个控制相机的会话，最后发送拍照、预览、录像等请求。

0 准备

1 新建工程，在一个Activity上

设置一个TextureView 用于预览图片；

设置一个ImageView 用于显示拍照结果；

设置一个 Button 用于触发拍照功能；

2 设置AndroidManifest.xml文件配置相机权限

<uses-permission android:name="android.permission.CAMERA" />
    <uses-permission android:name="android.permission.WRITE_EXTERNAL_STORAGE" />
    <uses-feature android:name="android.hardware.camera2.full" />

I 实现预览功能

1.先创建好一个预览的容器textureView

textureView=findViewById(R.id.texture_view_camera2);

监听这个容器的状态，如果容器准备好了，就开启相机：

// 先准备一个监听器
        surfaceTextureListener=new TextureView.SurfaceTextureListener() {
            @Override
            public void onSurfaceTextureAvailable(SurfaceTexture surface, int width, int height) {
                texture_surface=new Surface(textureView.getSurfaceTexture());
                openCamera();
            /.../
        //绑定监听器
        textureView.setSurfaceTextureListener(surfaceTextureListener);

启动相机时，要创建一系列的回调函数，所以应该从后向前写代码：

private void openCamera() {
      // 1 创建相机管理器，调用系统相机
        cameraManager= (CameraManager) getSystemService(Context.CAMERA_SERVICE); 
      // 2 准备 相机状态回调对象为后面用
        cam_stateCallback=new CameraDevice.StateCallback() {
            @Override
            public void onOpened(@NonNull CameraDevice camera) {
                // 2.1 保存已开启的相机对象
                opened_camera=camera;
                try {
                    // 2.2 构建请求对象（设置预览参数，和输出对象） 
                    requestBuilder = opened_camera.createCaptureRequest(CameraDevice.TEMPLATE_PREVIEW); // 设置参数：预览
                    requestBuilder.addTarget(texture_surface); // 设置参数：目标容器
                    request = requestBuilder.build();
                    //2.3 创建会话的回调函数，后面用
                    cam_capture_session_stateCallback=new CameraCaptureSession.StateCallback() {
                        @Override  //2.3.1  会话准备好了，在里面创建 预览或拍照请求
                        public void onConfigured(@NonNull CameraCaptureSession session) {
                            cameraCaptureSession=session;
                            try {
                                // 2.3.2 预览请求
                                session.setRepeatingRequest(request,null,null);
                            } catch (CameraAccessException e) {
                                e.printStackTrace();
                    // 2.3 创建会话
                    opened_camera.createCaptureSession( Arrays.asList(texture_surface), cam_capture_session_stateCallback,null);
                } catch (CameraAccessException e) {
                    e.printStackTrace();
            /..../
      // 4 检查相机权限 
        checkPermission();
      // 5 开启相机（传入：要开启的相机ID，和状态回调对象）
        try {
            cameraManager.openCamera(cameraManager.getCameraIdList()[0],cam_stateCallback,null);
        } catch (CameraAccessException




    
 e) {
            e.printStackTrace();
    }

4 申请相机权限

private void checkPermission() {
        // 检查是否申请了权限
        if(ContextCompat.checkSelfPermission(this, Manifest.permission.CAMERA)!= PackageManager.PERMISSION_GRANTED){
            if(ActivityCompat.shouldShowRequestPermissionRationale(this,Manifest.permission.CAMERA)){
            }else{
                ActivityCompat.requestPermissions(this,new String[]{Manifest.permission.CAMERA},1);
    }

II 实现拍照功能

这段代码都是在 Activity的onCreate里面写的。

准备ImageReader用于监听并接收相机拍摄的图片

//B1. 准备工作：初始化ImageReader
       imageReader = ImageReader.newInstance(1000  ,1000, ImageFormat.JPEG,2);

设置ImageReader的监听函数

//B2. 准备工作：设置ImageReader收到图片后的回调函数
        imageReader.setOnImageAvailableListener(new ImageReader.OnImageAvailableListener() {
            @Override
            public void onImageAvailable(ImageReader reader) {
                //B2.1 接收图片：从ImageReader中读取最近的一张，转成Bitmap
                Image image= reader.acquireLatestImage();
                ByteBuffer buffer= image.getPlanes()[0].getBuffer();
                int length= buffer.remaining();
                byte[] bytes= new byte[length];
                buffer.get(bytes);
                image.close();
                bitmap = BitmapFactory.decodeByteArray(bytes,0,length);
                //B2.2 显示图片
                takephoto_imageView.setImageBitmap(bitmap);
        },null);

保存ImageReader的Surface

//B3 配置：获取ImageReader的Surface
        imageReaderSurface = imageReader.getSurface();

设置相机的点击事件

//B4. 相机点击事件
        takephoto_btn.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                //B4.1 配置request的参数 拍照模式(这行代码要调用已启动的相机 opened_camera，所以不能放在外面
                try {
                    requestBuilder_image_reader = opened_camera.createCaptureRequest(CameraDevice.TEMPLATE_STILL_CAPTURE);
                } catch (CameraAccessException e) {
                    e.printStackTrace();
                requestBuilder_image_reader.set(CaptureRequest.JPEG_ORIENTATION,90);
                requestBuilder_image_reader.set(CaptureRequest.CONTROL_AF_TRIGGER, CameraMetadata.CONTROL_AF_TRIGGER_START);
                //B4.2 配置request的参数 的目标对象
                requestBuilder_image_reader.addTarget(imageReaderSurface );
                try {
                    //B4.3 触发拍照
                    cameraCaptureSession.capture(requestBuilder_image_reader.build(),null,null);
                } catch (CameraAccessException e) {
                    e.printStackTrace();
        });

最后要记得在之前配置的session会话里面绑定，当前这个输出对象imageReaderSurface：

private void openCamera() {
        /.../
        cam_stateCallback=new CameraDevice.StateCallback() {
            @Override
            public void onOpened(@NonNull CameraDevice camera) {
                    /.../
                    opened_camera.createCaptureSession( Arrays.asList(texture_surface,imageReaderSurface), cam_capture_session_stateCallback,null);
    }

这段功能的整体代码为：

@Override
    protected void onCreate(Bundle savedInstanceState) {
        /....../
        //B1. 准备工作：初始化ImageReader
        imageReader = ImageReader.newInstance(1000  ,1000, ImageFormat.JPEG,2);
        //B2. 准备工作：设置ImageReader收到图片后的回调函数
        imageReader.setOnImageAvailableListener(new ImageReader.OnImageAvailableListener() {
            @Override
            public void onImageAvailable(ImageReader reader) {
                //B2.1 接收图片：从ImageReader中读取最近的一张，转成Bitmap
                Image image= reader.acquireLatestImage();
                ByteBuffer buffer= image.getPlanes()[0].getBuffer();
                int length= buffer.remaining();
                byte[] bytes= new byte[length];
                buffer.get(bytes);
                image.close();
                bitmap = BitmapFactory.decodeByteArray(bytes,0,length);
                //B2.2 显示图片
                takephoto_imageView.setImageBitmap(bitmap);
        },null);
        //B3 配置：获取ImageReader的Surface
        imageReaderSurface = imageReader.getSurface();
        //B4. 相机点击事件
        takephoto_btn.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                //B4.1 配置request的参数 拍照模式(这行代码要调用已启动的相机 opened_camera，所以不能放在外面
                try {
                    requestBuilder_image_reader = opened_camera.createCaptureRequest(CameraDevice.TEMPLATE_STILL_CAPTURE);
                } catch (CameraAccessException e) {
                    e.printStackTrace();
                requestBuilder_image_reader.set(CaptureRequest.JPEG_ORIENTATION




    
,90);
                requestBuilder_image_reader.set(CaptureRequest.CONTROL_AF_TRIGGER, CameraMetadata.CONTROL_AF_TRIGGER_START);
                //B4.2 配置request的参数 的目标对象
                requestBuilder_image_reader.addTarget(imageReaderSurface );
                try {
                    //B4.3 触发拍照
                    cameraCaptureSession.capture(requestBuilder_image_reader.build(),null,null);
                } catch (CameraAccessException e) {
                    e.printStackTrace();
    }

III 相机的声明周期管理

1. 当activity不处于交互状态时释放相机

@Override
    protected void onPause() {
        // 先把相机的session关掉
        if(cameraCaptureSession!=null){
            cameraCaptureSession.close();
        // 再关闭相机
        if(null!=opened_camera){
            opened_camera.close();
        // 最后关闭ImageReader
        if(null!=imageReader){
            imageReader.close();
        // 最后交给父View去处理
        super.onPause();
    }

2 当活动再次可以交互时开启相机

@Override
    protected void onResume() {
        super.onResume();
        // 如果 textureView可用，就直接打开相机
        if(textureView.isAvailable()){
            openCamera();
        }else{
        // 否则，就开启它的可用时监听。
            textureView.setSurfaceTextureListener(surfaceTextureListener);
    }

IV 预览和功能的完整代码为：

文件名 Camera2ApiActivity.java

package com.example.myapplication;
import androidx.annotation.NonNull;
import androidx.appcompat.app.AppCompatActivity;
import androidx.camera.camera2.impl.Camera2CaptureRequestBuilder;
import androidx.camera.core.CameraCaptureResult;
import androidx.core.app.ActivityCompat;
import androidx.core.content.ContextCompat;
import android.Manifest;
import android.content.Context;
import android.content.pm.PackageManager;
import android.graphics.Bitmap;
import android.graphics.BitmapFactory;
import android.graphics.ImageFormat;
import android.graphics.SurfaceTexture;
import android.hardware.biometrics.BiometricManager;
import android.hardware.camera2.CameraAccessException;
import android.hardware.camera2.CameraCaptureSession;
import android.hardware.camera2.CameraDevice;
import android.hardware.camera2.CameraManager;
import android.hardware.camera2.CameraMetadata;
import android.hardware.camera2.CaptureFailure;
import android.hardware.camera2.CaptureRequest;
import android.hardware.camera2.CaptureResult;
import android.hardware.camera2.TotalCaptureResult;
import android.media.Image;
import android.media.ImageReader;
import android.os.Bundle;
import android.util.Size;
import android.view.Surface;
import android.view.TextureView;
import android.view.View;
import android.widget.Button;
import android.widget.ImageView;
import java.io.ByteArrayInputStream;
import java.nio.Buffer;
import java.nio.ByteBuffer;
import java.util.ArrayList;
import java.util.Arrays;
public class Camera2apiActivity extends AppCompatActivity {
    TextureView textureView;
    TextureView.SurfaceTextureListener surfaceTextureListener;
    CameraManager cameraManager;
    CameraDevice.StateCallback cam_stateCallback;
    CameraDevice opened_camera;
    Surface texture_surface;
    CameraCaptureSession.StateCallback cam_capture_session_stateCallback;
    CameraCaptureSession.CaptureCallback still_capture_callback;
    CameraCaptureSession cameraCaptureSession;
    CaptureRequest.Builder requestBuilder;
    CaptureRequest.Builder requestBuilder_image_reader;
    ImageReader imageReader;
    Surface imageReaderSurface;
    Bitmap bitmap;
    CaptureRequest request;
    CaptureRequest takephoto_request;
    Button takephoto_btn;
    ImageView takephoto_imageView;
    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_camera2api);
        textureView=findViewById(R.id.texture_view_camera2);
        takephoto_btn=findViewById(R.id.btn_camera2_takephoto);
        takephoto_imageView= findViewById(R.id.image_view_preview_image);
        surfaceTextureListener=new TextureView.SurfaceTextureListener() {
            @Override
            public void onSurfaceTextureAvailable(SurfaceTexture surface, int width, int height) {
                texture_surface=new Surface(textureView.getSurfaceTexture());
                openCamera();
            @Override
            public void onSurfaceTextureSizeChanged(SurfaceTexture surface, int width, int height) {
            @Override
            public boolean onSurfaceTextureDestroyed(SurfaceTexture surface) {
                return false;
            @Override
            public void onSurfaceTextureUpdated(SurfaceTexture surface) {
        textureView.setSurfaceTextureListener(surfaceTextureListener);
        //B1. 准备工作：初始化ImageReader
        imageReader = ImageReader.newInstance(1000  ,1000, ImageFormat.JPEG,2);
        //B2. 准备工作：设置ImageReader收到图片后的回调函数
        imageReader.setOnImageAvailableListener(new ImageReader.OnImageAvailableListener() {
            @Override
            public void onImageAvailable(ImageReader reader) {
                //B2.1 接收图片：从ImageReader中读取最近的一张，转成Bitmap
                Image image= reader.acquireLatestImage();
                ByteBuffer buffer= image.getPlanes()[0].getBuffer();
                int length= buffer.remaining();
                byte[] bytes= new byte[length];
                buffer.get(bytes);
                image.close();
                bitmap = BitmapFactory.decodeByteArray(bytes,0,length);
                //B2.2 显示图片
                takephoto_imageView.setImageBitmap(bitmap);
        },null);
        //B3 配置：获取ImageReader的Surface
        imageReaderSurface = imageReader.getSurface();
        //B4. 相机点击事件
        takephoto_btn.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                //B4.1 配置request的参数 拍照模式(这行代码要调用已启动的相机 opened_camera，所以不能放在外面
                try {
                    requestBuilder_image_reader = opened_camera.createCaptureRequest(CameraDevice.TEMPLATE_STILL_CAPTURE);
                } catch (CameraAccessException e) {
                    e.printStackTrace();
                requestBuilder_image_reader.set(CaptureRequest.JPEG_ORIENTATION,90);
                requestBuilder_image_reader.set(CaptureRequest.CONTROL_AF_TRIGGER, CameraMetadata.CONTROL_AF_TRIGGER_START);
                //B4.2 配置request的参数 的目标对象
                requestBuilder_image_reader.addTarget(imageReaderSurface );
                try {
                    //B4.3 触发拍照
                    cameraCaptureSession.capture(requestBuilder_image_reader.build(),null,null);
                } catch (CameraAccessException e) {
                    e.printStackTrace();
    private void openCamera() {
        cameraManager= (CameraManager) getSystemService(Context.CAMERA_SERVICE);  // 初始化
        cam_stateCallback=new CameraDevice.StateCallback() {
            @Override
            public void onOpened(@NonNull CameraDevice camera) {
                opened_camera=camera;
                try {
                    requestBuilder = opened_camera.createCaptureRequest(CameraDevice.TEMPLATE_PREVIEW);
                    requestBuilder.addTarget(texture_surface);
                    request = requestBuilder.build();
                    cam_capture_session_stateCallback=new CameraCaptureSession.StateCallback() {
                        @Override
                        public void onConfigured(@NonNull CameraCaptureSession session) {
                            cameraCaptureSession=session;
                            try {
                                session.setRepeatingRequest(request,null,null);
                            } catch (CameraAccessException e) {
                                e.printStackTrace();
                        @Override
                        public void onConfigureFailed(@NonNull CameraCaptureSession session) {
                    opened_camera.createCaptureSession( Arrays.asList(texture_surface,imageReaderSurface), cam_capture_session_stateCallback,null);
                } catch (CameraAccessException e) {
                    e.printStackTrace();
            @Override
            public void onDisconnected(@NonNull CameraDevice camera) {
            @Override
            public void onError(@NonNull CameraDevice camera, int error) {
        checkPermission();
        try {
            cameraManager.openCamera(cameraManager.getCameraIdList()[0],cam_stateCallback,null);
        } catch (CameraAccessException e) {
            e.printStackTrace();
    private void checkPermission() {
        // 检查是否申请了权限
        if(ContextCompat.checkSelfPermission(this, Manifest.permission.CAMERA)!= PackageManager.PERMISSION_GRANTED){
            if(ActivityCompat.shouldShowRequestPermissionRationale(this,Manifest.permission.CAMERA)){
            }else{
                ActivityCompat.requestPermissions(this,new String[]{Manifest.permission.CAMERA},1);
        @Override
    protected void onResume() {
        super.onResume();
        // 如果 textureView可用，就直接打开相机
        if(textureView.isAvailable()){
            openCamera();
        }else{
        // 否则，就开启它的可用时监听。
            textureView.setSurfaceTextureListener(surfaceTextureListener);
        @Override
    protected void onPause() {
        // 先把相机的session关掉
        if(cameraCaptureSession!=null){
            cameraCaptureSession.close();
        // 再关闭相机
        if(null!=opened_camera){
            opened_camera.close();
        // 最后关闭ImageReader
        if(null!=imageReader){
            imageReader.close();